The object of this reasearch is to bring a bearing on the techniques of Mossbauer spectroscopy and susceptometry on a number of problems in the study hemoproteins and synthetic analogues which mimic their properties. The Mossbauer apparatus is in place and working; the susceptometer is in an advanced stage of construction, but needs some modification to improve its stability and noise performance. Techniques and computer programs for Mossbauer interpretation are in hand but will be further developed and extended to the closely related calculation of susceptibilities (this has already been done in many cases). A large body of available data on deoxyhemes has failed to yield satisfactory quantum mechanical interpretation. Mossbauer and to some extent susceptibility data will be acquired on polycrystalline and single crystal heme model compounds as well as other instructive high spin ferrous materials. Renewed efforts to provide theoretical interpretation will be based on Mossbauer, susceptibility, IR, and NMR data. The nature of deoxyhemes will be probed by both Mossbauer and susceptometry, repeating some of the published experiments in which paramagnetism was found. A central aspect will be the correlation between changes in Mossbauer spectra and the onset of paramagnetism, both of which seem to have the same characteristic temperature dependence. Comparison of normal oxhemoglobin with that of opossum will be made: the latter exhibits higher characteristic temperature in Mossbauer measurements. Efforts to detect effects on the active site in hemoglobin of the R to T quaternary transformation will continue, most probably involving isotopically enriched fish tetramers. A variety of problems involving unusual spin states and coupled spin systems (relevant to the peroxidase intermediates) will be pursued, mostly by measuring and interpreting high magnetic field Mossbauer spectra of synthetic analogues. An understanding of the action of heme proteins is important because of their direct importance in the metabolism of humans and most other animals and because they serve as good models in the study of enzymatic action and regulation mechanisms of biomolecules in general. The long term relevance of such understanding of health problems is well-established.